1. Field of the Invention
The present invention relates to a switch-equipped input-output plug, and in particular, it relates to an improvement of a switch-equipped 3-electrode/4-electrode shared input-output plug.
2. Description of the Related Art
Hitherto, a switch-equipped earphone microphone of a portable phone has an input-output terminal different one carrier from another or one type of portable phone from another. The input-output terminals are generally classified into a 3-electrode jack type having a diameter of 2.5 mm and being available for a 3-electrode plug; and a 4-electrode jack type formed by adding a fourth terminal to the outer surface of the 3-electrode jack type.
The above-described 3-electrode and 4-electrode plugs are disclosed in detail in Japanese Registered Utility Model No. 3036532 (see FIGS. 1 to 4, hereinafter, referred to as Patent Document 1). When such a known 3- or 4-electrode plug is used for a voice input-output apparatus (for example, a switch-equipped earphone microphone), an input-output operation of voice of a voice output apparatus (earphone microphone) or a voice input apparatus (earphone or head phone) is controlled in accordance with an on/off operation of a switch by using a switch circuit.
Unfortunately, the known switch-equipped earphone microphone is required to use a 3-electrode or 4-electrode plug depending on the type of an input-output terminal of an electronic device installed in a portable phone or the like (in other words, depending on the type of a portable phone or the like); hence a single type of a switch-equipped earphone microphone is not commonly available for portable phones or the like made by different manufacturers.
In order to solve the above-described problem, Patent Document 1 discloses a switch-equipped 3-electrode/4-electrode shared input-output plug available for a switch-equipped earphone microphone even when the type of an input-output terminal of an electronic device installed in a portable phone or the like is different one portable phone from another.
FIG. 5A is a side view a 3-electrode/4-electrode shared plug 10 disclosed in Patent Document 1, and FIG. 5B is a partial side sectional view of the 3-electrode/4-electrode shared plug 10.
As shown in FIGS. 5A and 5B, the 3-electrode/4-electrode shared plug 10 includes (i) a column-shaped pin portion 6 integrally formed by synthetic resin insulators 5 serving as forming members and insulating one of three electrodes of a microphone electrode (input electrode) 1, an earphone or loudspeaker electrode (output electrode) 2, and a ground electrode 3 from the remaining ones; (ii) a base portion 7 having the pin portion 6 fixed to one end thereof; (iii) a grooved portion 8 disposed at the one end of the base portion 7, and having a greater diameter than that of the pin portion 6; (iv) terminals 9 formed in the grooved portion 8; (v) four lines a to d disposed in the base portion 7, respectively connected or bonded, in the base portion 7, to the three electrodes 1 to 3, and to one of the terminals 9, extending outside the base portion 7 from the other end of the base portion 7; and (vi) and an adaptor 4 (see FIG. 6). The grooved portion 8 is formed so as to be fitted into or screwed with the adaptor 4, and the terminals 9 are formed so as to be connected with the adaptor 4 at the bottom or the side of the inside of the grooved portion 8. A cord 12 has the four lines a, b, c, and d included therein, extending outside from the other end of the base portion 7.
Meanwhile, in the plug 10 shown in FIGS. 5A and 5B, since the adaptor 4 serving as a fourth electrode is not fitted into or screwed with the grooved portion 8, the voltage of the line d connected to one of the terminals 9 is zero. Accordingly, the plug 10 serves as a 3-electrode plug in which the three electrodes of the microphone electrode 1, the earphone or loudspeaker electrode 2, and the ground electrode 3 function.
FIGS. 6A and 6B illustrate an example structure of the adaptor 4 serving as the fourth electrode.
As shown in FIGS. 6A and 6B, the adaptor 4 has a space (or through-hole) 43 similar to the normal cross-section of the pin portion 6, formed therein so as to have the pin portion 6 of the 3-electrode/4-electrode shared plug 10 loosely fitted thereinto. Since the normal cross-section of the pin portion 6 shown in FIGS. 6A and 6B has a round shape, the normal cross-section of the space (or the through) 43 shown in FIGS. 6A and 6B has a round shape accordingly.
When the adaptor 4 is formed so as to be fitted into the grooved portion 8 as shown in FIG. 6A, the outer shape (normal cross-section) of the adaptor 4 is not limited to a specific one, and it may be a round or a polygon. When the adaptor 4 is formed so as to have a thread groove 45 formed therearound and to be screwed into the grooved portion 8 as shown in FIG. 2B, its the outer shape (normal cross-section) is a round (that is, in this case, the adaptor 4 has a ring shape).
Grooves 41 and 42 shown in FIG. 6A, formed in the adaptor 4, are detent grooves preventing the adaptor 4 from moving back when the adaptor 4 is fitted into the grooved portion 8.
Meanwhile, the adaptor 4 shown in FIGS. 6A and 6B is processed so as to have an electrically insulated inside, for example, by bonding a synthetic resin onto the inside by pressing, or a portion of the adaptor 4 of the pin portion 6, coming contact with the grooved portion 8 when the adaptor 4 is fitted into or screwed with the grooved portion 8, is subjected to an insulating process.
FIG. 7 is a side view of the plug 10 in a state in which the adaptor 4 shown in FIGS. 6A and 6B is fitted into or screwed with the grooved portion 8 shown in FIGS. 5A and 5B. The adaptor 4 is inserted from the top of the pin portion 6 toward the base portion 7 and fitted into or screwed with the grooved portion 8. In this case, since the top or the side of the adaptor 4 comes into contact with and is connected with the terminals 9 disposed at the bottom or the side of the grooved portion 8, the adaptor 4 is connected with the line d through one of the terminals 9 and serves as a manipulate-signal electrode. Accordingly, the plug 10 serves as a 4-electrode plug in which four electrodes of the microphone electrode 1, the earphone or loudspeaker electrode 2, the ground electrode 3, and the manipulate-signal electrode (adaptor) 4 function.
FIG. 8 is a diagram of a switch circuit 100 of a switch-equipped voice input-output device (for example, a switch-equipped earphone microphone) including the above-described 3-electrode/4-electrode shared plug 10.
As shown in FIG. 8, the switch circuit 100 is made up by the line a connected with the microphone electrode 1 at one end thereof and with a first terminal of a microphone 101 at the other end thereof; the line b connected with the earphone electrode 2 at one end thereof and with a first terminal of an earphone 102; the line c connected with the ground electrode 3 at one end thereof and having a contact 103B of a switch unit 103 at the other end thereof, and connecting a line a′ extending from a second terminal of the microphone 101 and a line b′ extending from a second terminal of the earphone 102 with each other; the line d connected with the manipulate-signal electrode 4 at one end thereof and having a contact 103A of the switch unit 103; and a blocking diode 104 disposed between the lines b and d, connected with the ground electrode 3 at one end thereof, with a current direction from the line b to the line d as a forward direction.
With above structure, in the 3-electrode/4-electrode shared plug 10, when the adaptor 4 is not fitted into or screwed with the grooved portion 8, and when the 3-electrode/4-electrode shared plug 10 is inserted into a normal recessed connector (jack) of a portable phone or the like, the voltage of the line d becomes zero; hence the switch unit 103 performs an on/off operation between the lines b and c and thus can perform a reception/transmission operation in accordance with the on/off operation, whereby the switch circuit 100 serves a switch circuit of a 3-electrode plug.
Also, in the 3-electrode/4-electrode shared plug 10 has a structure, when the adaptor 4 is moved toward the base portion of the pin portion 6 and is fitted into or screwed with the grooved portion 8 so as to serve as a manipulate-signal electrode, and when the pin portion 6 is inserted into a connecting hole of a RC connector of an electronic device installed in a portable phone or the like until the upper part of the RC connector comes into contact with the adaptor 4, since the voltage of the line d becomes higher than that of the line b, and the switch unit 103 performs on/off operation between the lines d and c and hence can perform a reception/transmission operation in accordance with the on/off operation, whereby the switch circuit 100 serves as switch circuit of a 4-electrode plug.
Although the switch-equipped 3-electrode/4-electrode shared plug having the foregoing known structure is available for any one of two type of portable phones; one having 3-electrode jack and the other having a 4-electrode jack, since adaptor 4 serving as a manipulate-signal electrode is fitted into or screwed with the grooved portion 8 formed by machining the base portion 7, through which the cord 12 making up a 3-electrode plug extends outside, it is difficult to fit the grooved portion 8 into the adaptor 4 because of a thin wall of the adaptor 4, as a result, the pin portion 6 is likely detached from the base portion 7.
Also, in some portable phones, since a jack fixed to a casing lies on a part of a chassis lying deep inside the casing, and also, a gap exists between the casing and the chassis, the pin portion 6 of a 3-electrode plug, having a standard length, cannot be inserted into the jack to its full length so that the root thereof comes into contact with the jack, thereby sometimes causing poor contact.